Serum Sodium Changes in Fluoxetine Users at Different Age Groups

Article excerpt

Objective: Fluoxetine, a widely used antidepressant, can affect the serum sodium level. The aim of this study was to evaluate and compare changes in the serum sodium level of depressive patients taking fluoxetine according to age.

Methods: This quasi-experimental study was conducted on 126 patients with depression, dividing the patients into two age groups of 15 to 35 years, and above 55 years, who referred to psychiatric clinics of the Isfahan University of Medical Sciences. Serum sodium level was measured prior to fluoxetine therapy and at the first and third week after; adverse symptoms were recorded. Serum sodium level, hyponatremia, and other adverse effects were compared between the two age groups.

Results: There was a significant decrease in serum sodium levels in the older patients at the first and third week after the therapy; but the serum sodium levels decreased only after the third week of therapy in the younger patients (p < 0.05). Serum sodium level was significantly lower in older than in younger patients at the third week of the therapy (140.8±2.26 vs. 135.2±2.06; p < 0.05), and hyponatremia was detected only in the older patients after the first and third week of therapy, 4.7% and 15.8%, respectively.

Conclusions: Using fluoxetine can decrease serum sodium level, which is more frequent, more severe, and more clinically manifested in older than younger patients. Monitoring serum sodium level is recommended in early weeks of fluoxetine therapy especially for patients older than 55 years of age.

Selective serotonin reuptake inhibitors (SSRIs) are among the most common antidepressants that are increasingly used by young, adult, and elderly patients (1). Fluoxetine is a SSRI with good efficacy, few adverse effects, long half life, good compliance, and low depression relapse rate after it is discontinued, and it is also a drug of choice in elderly depressive patients (1,2.( Recent studies have reported that hyponatremia and syndrome of inappropriate anti-diuretic hormone (SIADH) are more frequent in fluoxetine than in other SSRIs users (3-5), and in older patients than in younger ones (4-7). The incidence of hyponatremia in elderly patients treated with fluoxetine is 5/1000 per year (8) that reaches to maximum of 8/1000 in elderly women (7). Hyponatremia and SIADH can cause such complications as seizure, coma, and rarely death for fluoxetine users (6,9,10).

The prevalence of hyponatremia in Iranian patients with depression, who may have different drug metabolism and take fluoxetine, is still unclear. Our aim was to compare side effects of fluoxetine therapy through any changes in the serum sodium level , and its adverse symptoms in patients at different age groups.

Materials and Methods

In a quasi-experimental study with stratified random sampling method, patients with depression referring to Sadeghieeh Elderly House and psychiatric clinics of Noor University Hospital, Isfahan (IRAN) were selected. Inclusion criteria were as follows: age between 15 and 35 or above 55 years; indication for fluoxetine prescription (20 mg/d) due to new onset depression (1); and new administration of fluoxetine. Patients with history of previous SSRI therapy, those using other psychiatric or diuretic drugs, and those with known diseases affecting serum sodium level (e.g. impaired renal function, heart failure, hypothyroidism, etc.) were not included. Compliance of the patients was checked by their associate physicians, and non-compliant patients were excluded.

In a single clinical laboratory, serum sodium level was tested for each patient before fluoxetine administration and at first and third week after fluoxetine therapy. The study was approved by Research Ethics Committee of the Isfahan University of Medical Sciences, and consent was obtained from all patients. …